Jen Christiansen
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In Brief
- Red and green are called opponent colors because people normally cannot see redness and greenness simultaneously in a single color. The same is true for yellow and blue.
- Researchers have long regarded color opponency to be hardwired in the brain, completely forbidding perception of reddish green or yellowish blue.
- Under special circumstances, though, people can see the “forbidden” colors, suggesting that color opponency in the brain has a softwired stage that can be disabled.
- In flickering light, people see a variety of geometric hallucinations with properties suggestive of a geometric opponency that pits concentric circles in opposition to fan shapes.
Engineers often load a structure with weight until it collapses or shake it until it flies apart. Like engineers, many scientists also have a secret love for destructive testing—the more catastrophic the failure, the better. Human vision researchers avoid irreversible failures (and lawsuits) but find reversible failures fascinating and instructive—and sometimes even important, as with the devastating spatial disorientations and visual blackouts that military pilots can experience. At the U.S. Air Force Research Laboratory, the two of us explore the most catastrophic visual failures we can arrange. We create conditions in which people see images flowing like hot wax and fragmenting like a shattered mosaic. Here, we tell the story of the two most intriguing perceptual breakdowns we have studied: forbidden colors and biased geometric hallucinations.
Have you ever seen the color bluish yellow? We do not mean green. Some greens may appear bluish and others may appear yellow-tinged, but no green (or any other color) ever appears both bluish and yellowish at the same moment. And have you ever seen reddish green? We do not mean the muddy brown that might come from mixing paints, or the yellow that comes from combining red and green light, or the texture of a pointillist’s field of red and green dots. We mean a single color that looks reddish and greenish at the same time, in the same place.
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18 Comments
Add CommentI was able to see reddish green by simply taking two color swatches I had laying around for house paint. I placed one swatch in front of each eye. One red swatch plus one green swatch and Voila! Reddish green. Thank you for making my day!
Reply | Report Abuse | Link to thisWould someone try to describe the red-green forbidden color. Using the binocular sample labled "Can You See IT?" on page 77 I had no problem seeing a combination block with the pluses coincidental (I was also seeing the red block to the right and the green to the left) with the combination block stable in the middle. I would describe the color impression as a rather weak lavender. I expected to see a new color as vivid as turquoise. What I saw was pretty washed out and similar to center of the "B" image on page 75. I would be interested in other peoples impression of the "Can You See It?" experiment.
Reply | Report Abuse | Link to thisEnter YA few comments and questions re Seeing forbidden colors.
Reply | Report Abuse | Link to this1. Whose term is forbidden? The first time in the text it is written straight, the second time in quotation marks.
2. In the text Herings theory is dated as of 1872; in the top box of pg 74 as of 1897.
3. What is the scientific basis of the figure of the opponent functions in the top box pg. 74? In what sense can it be said that these curves predict the hues of the visible spectrum? At 400 and 700 nm the channel responses are near zero yet the colors in the spectrum are intensely violet or red. The responses of opponent cells in the LGN of the brain are not modeled by these curves. At the same time it is evident that unique hues are not directly modeled by LGN cell functions. There is as yet no believable neurophysiological model for hue perception.
4. Who are the other five vision scientists that did the experiment? Did they not want to be named? If so why not?
5. The authors say that the viewers often saw a nice reddish green or bluish yellow fill the whole field. Are these new hues? Nobody made an effort to try to describe such hues in some more detail? Is the grayish color in field B of the pg. 75 box an indication of what it looks like?
6. I have viewed adjacent pairs of large sheets of uniformly colored paper of similar luminous reflectance using a simple stereoptic viewer (black plastic frame with two plastic lenses). The result is three rectangular fields: left and right fields with the colors of the papers, but appearing much more intense, almost self-luminous; in the middle a field, depending on small movements, either red or green predominate. Exactly centered, the field appears in a dull brownish, but lighter color: what might be the additive mixture of the stimuli coming from the two papers. It is reminiscent of what is shown in field. B. What am I missing in generating red-green, or is this it?
7. Is there going to be a scientific paper on this subject that provides more detail?
Red and Green are not opposites on the color wheel the way blue & yellow are, they are only 120 degrees apart. Blue & yellow cancel to white or black, depending on additive or subtractive method. Red & Green make yellow or brown(dark yellow).
Reply | Report Abuse | Link to thisRed and Green are not opposites on the color wheel the way blue & yellow are, they are only 120 degrees apart. Blue & yellow cancel to white or black, depending on additive or subtractive method. Red & Green make yellow or brown(dark yellow).
Reply | Report Abuse | Link to thisIn the "scientific" literature, color is often identified with wavelength -- as part of what "everybody knows.
Reply | Report Abuse | Link to thisThis, despite the fact that colors behave like vectors, as Maxwell, Weyl, Schrodinger and Feynman tell us, and as our color TVs and computer monitors demonstrate.
Whereas a wavelength, being a length, is a scalar.
The situation remains much the same as Whitehead described it, a century ago:
What we see depends on light entering the eye. Furthermore we do not even perceive what enters the eye. The things transmitted are waves or—as Newton thought—minute particles, and the things seen are colors. Locke met this difficulty by a theory of primary and secondary qualities. Namely, there are some attributes of the matter which we do perceive. These are the primary qualities, and there are other things which we perceive, such as colors, which are not attributes of matter, but are perceived by us as if they were such attributes. These are the secondary qualities of matter.
Why should we perceive secondary qualities? It seems an unfortunate arrangement that we should perceive a lot of things that are not there. Yet this is what the theory of secondary qualities in fact comes to. There is now reigning in philosophy and in science an apathetic acquiescence in the conclusion that no coherent account can be given of nature as it is disclosed to us in sense-awareness, without dragging in its relation to mind.
Whitehead, 'The Concept of Nature,' www.gutenberg.org/files/18835/18835-h/18835-h.htm
In the "scientific" literature, color is often identified with wavelength -- as part of what "everybody knows.
Reply | Report Abuse | Link to thisThis, despite the fact that colors behave like vectors, as Maxwell, Weyl, Schrodinger and Feynman tell us, and as our color TVs and computer monitors demonstrate.
Whereas a wavelength, being a length, is a scalar.
The situation remains much the same as Whitehead described it, nearly a century ago:
What we see depends on light entering the eye. Furthermore we do not even perceive what enters the eye. The things transmitted are waves or—as Newton thought—minute particles, and the things seen are colors. Locke met this difficulty by a theory of primary and secondary qualities. Namely, there are some attributes of the matter which we do perceive. These are the primary qualities, and there are other things which we perceive, such as colors, which are not attributes of matter, but are perceived by us as if they were such attributes. These are the secondary qualities of matter.
Why should we perceive secondary qualities? It seems an unfortunate arrangement that we should perceive a lot of things that are not there. Yet this is what the theory of secondary qualities in fact comes to. There is now reigning in philosophy and in science an apathetic acquiescence in the conclusion that no coherent account can be given of nature as it is disclosed to us in sense-awareness, without dragging in its relation to mind.
Whitehead, Alfred North. 'The Concept of Nature,' Cambridge, 1920.
www.gutenberg.org/files/18835/18835-h/18835-h.htm
Oh, I thought they meant the light-grey text in the comment box...
Reply | Report Abuse | Link to thisWhat a flawed study and flawed set of assumptions. Flickering blue and yellow and processing them both does not in any way constitute a new color. It is just both in a small scale of time. Not the same experience or neural correlate.
Reply | Report Abuse | Link to thisRed's complimentary (opposite) color is CYAN (equal blue and green). While a few might seen cyan as greenish, most describe it as bluish.
Reply | Report Abuse | Link to thisReddish-green is called "Brown".
Reply | Report Abuse | Link to thisYellowish-blue is called "Green".
Questions?
Reddish-green is called "Brown".
Reply | Report Abuse | Link to thisYellowish-blue is called "Green".
For pigment (subtractive), yes.
In light (additive), red + green = yellow, a secondary.
R+B=Magenta
B+G=Cyan
From BRG (RGB) you can obtain YCM and vice versa.
A second item on the list of what "everybody knows" concerns quantum theory -- and is highly relevant here.
Reply | Report Abuse | Link to thisAs we read in Byron & Fuller, e.g., "Axiom I. Any physical system is completely described by a normalized vector (the state vector or wave function) in Hilbert space. All possible information about the system can be derived from this state vector by rules..."
Yet the author of the wave function evidently disagreed:
"If you ask a physicist what is his idea of yellow light, he will tell you that it is transversal electromagnetic waves of wavelength in the neighborhood of 590 millimicrons. If you ask him: But where does yellow come in? he will say: In my picture not at all, but these kinds of vibrations, when they hit the retina of a healthy eye, give the person whose eye it is the sensation of yellow." (Schrödinger)
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The seminal papers in the field can be found in 'Selected Papers on Colorimetry--Fundamentals' (SPIE Press Book)
Artists can do this at will...I laughed when I read the article...Just the other day I was talking about this very thing. It is a knack that painters who work with colour daily learn to do..to break down the component down to subcomponents. It works best with pigment but even RGB images can be analyzed that way ( I almost wrote Grok-ed that way as for those in the know, some of us can do things that others cannot) What is possible is that the brain is plastic and can learn new things and/or some of us simply have it built in. I do not claim uniqueness in this as many artists can do this and do not even discuss it as it is, well, what we do.
Reply | Report Abuse | Link to thisWhen fusing the two patches, they do not appear to be patchy or unstable. Instead, the fused patch appears to be a light olive brown that is at about half the saturation of either the red or the green viewed individually. This image is the same whether viewed as cross-view (converged far enough so that the left eye views the right image and the right eye views the left image), or viewed close to parallel (converged only slightly, so that the left eye views the left image and the right eye views the right image). If I could send a picture, I could show you the image as it appears.
Reply | Report Abuse | Link to thisYou might also want to investigate some other related visual phenomena, including the effect of rod and cone opponency as light levels decrease, and the effects of differential stereopsis on left-eye-to-right-eye color perception.
thanks, all.
Reply | Report Abuse | Link to thisvery true comments.
being a believer in the infinity of color above all matter and mass, it seems most happy that they will not be lost.
I think this amounts to complementary colour vision as demonstrated by many experiments. E. g. Concentrating on red colour for couple of minutes and then putting it off shows green colour.
Reply | Report Abuse | Link to thisKiran P. Prayagi
@silvrhairdevil
Reply | Report Abuse | Link to thisNo, they aren't, get your facts straight. Reddish green and yellowish blue are colors that we as trichromats are unable to see; our brain only gets confused and shows us brown and green in their places.